Property Damage can also occur when there is upward movement of the ground supporting the building – this is known as heave. Both subsidence and heave are usually covered under standard building’s insurance policy.

Is it a problem?

Although not widely recognised, subsidence is a real threat for home owners:

  • Over the last 10 years subsidence has cost the economy an estimated £3bn, making subsidence the most damaging geohazard in Britain today (Jones 2006*).
  • As many as one in five homes in England and Wales are likely to be damaged by ground that swells when it gets wet and shrinks as it dries out (Jones 2006*).
  • Subsidence affects as many properties in the UK on an annual basis as floods.
  • European research predicts a 50% increase in subsidence by 2040. This follows an actual 50% increase in subsidence we have seen today compared with the period 1951-1970
  • If the property has had a subsidence insurance claim or has suffered historically from subsidence, it must be declared on the solicitor’s disclosure form and as such may affect the buyer’s ability to secure a mortgage on the property.

If you are looking to purchase a property it is advisable to make sure your conveyancer or solicitor checks the risk of subsidence within their searches.

The good news is that unlike other geohazards some relatively easy and cost effective steps can reduce the risk of subsidence.

*Dr Lee Jones, Engineering Geologist at the British Geological Survey

 

Are all cracks in houses caused by subsidence?

Cracks in houses can be caused by a range of issues other than subsidence – some house cracks are related to normal wear and tear due to the age and construction of the property, and other, non-foundation related structural issues which are not traditionally covered by buildings insurance.

The other main causes of cracks in houses are:

Settlement after construction
When a property is built its weight may cause the ground to consolidate and lose volume.
Thermal expansion and contraction of materials
Modern, rigid structures have less ability to expand and contract from changes in temperatures. Block work (which is generally used as the inner skin in most modern external cavity walls) is particularly prone to this effect and results in vertical cracking. Other materials prone to temperature shrinkage are modern mortars (cement based), re-constituted stonework, concrete lintels over windows and doors, metal and steel lintels and beams, timber and even plasterboard ceilings.
Lintel failure
Lintels support the walls above windows and doors. They can deteriorate over time resulting in a weakening of the lintel with resulting movement of the supported wall. Cracks usually appear above the window/door opening.
Chemical attack
This happens in chimneys where the chemicals in the gases from the fire (sulphates) attack the brickwork. This leads to expansion and vertical cracking of the chimney stack.
Roof spread
If the roof is poorly constructed, or if there has been structural deterioration, or has seen an increase in weight (such as the installation of Solar Panels) for which it was not designed to carry, then the roof may push the walls outwards resulting in cracking.
Wall tie failure
Wall ties bind together cavity walls. They can corrode and expand pushing out the external wall and resulting in horizontal cracking.

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Further information

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